Precise and adaptive regulation of system pressures and the mass flow of gas lines can make all the difference in developing an efficient hydrogen fuel cell system. In this article, we cover the various sensing technologies in fuel cell applications and discuss how mass flow and pressure devices are used to optimize these technologies.

Fast and accurate instruments throughout the fuel cell system make life much easier when conducting PEM fuel cell testing and diagnosis. Alicat instrument’s expansive turndown ratios allow processes to be easily scaled through the development process.

Regulating oxidant and reactant ratios and distributions across gas diffusion layers of stacks is key to maintaining the efficiency of hydrogen fuel cell technology. Using an MFC with setpoint stabilization times as fast as 30 milliseconds, reliable and fast-responding flow control becomes an invaluable reality in fuel cell test benches.

When process conditions include high pressures and low flow rates, a Coriolis mass flow controller is a reliable, high-accuracy option. For higher flow rates of mainline inputs and outputs, a differential pressure (DP) mass flow controller can be used to monitor both pressure and mass flow simultaneously over a wide range of flow rates. It is also important to maintain tight back pressure control, which can be difficult in environments with high temperature, high humidity, and moisture. To accommodate those conditions, a dome loaded pressure regulator will respond well to a pilot pressure controlled by an Alicat dual-valve pressure controller.

As is also the case in electrolysis, a multi-orifice back pressure regulator is well suited to maintain ideal reaction conditions in fuel cell systems, allowing pressure regulation down to 0.0001 PSIG in most testing conditions. Using stainless steel DP mass flow meters provide fast and accurate mass flow readings, unaffected by moisture passing through the unit.

Yet another challenge is regulating temperature across the stack. Well-regulated temperatures maintain a consistent rate of power distribution. Insufficient regulation can cause efficiency losses and even damage to the stack elements. Those challenges become increasingly more difficult as the number of cells increase in the stack. Incorporating differential pressure mass flow controllers with ≥30 ms response times and turndown ratios as good as 10,000:1, fast, stable temperature regulation is achievable because each instrument reports process temperature at its point in the process. These MFCs can function as hydrogen mass flow controllers, or be switched in situ to remain fully accurate metering any of 97 other pure gases, or a custom gas mix you choose.

Humidification is equally important to ensure efficient proton conductivity across the electrolyte layer as an excess or deficit of water can greatly impact fuel cell efficiency.

Once optimal stoic, flow rates, pressure, and temperatures have been established, Alicat solutions can be used to regulate flow and pressure, and monitor temperature in your finished fuel cell systems.

Pressure regulation units can be used in combination with external sensors to regulate pressure upstream of the sensor position. In high temperature, high humidity lines, remote sensors and valves can also be employed for pressure regulation. Fast response times and turndown ratios of up to 10,000:1 ensure that pressure and mass flow controllers can precisely control hydrogen flow into pre-heating systems and maintain fuel cell system efficiency. Meanwhile, a multi-orifice back pressure regulator maintains exhaust gas output.

Leak checking fuel cell systems – especially membrane leak and permeability testing – is vital. Performing a leak test ensures consistent flow rates, maintains process efficiency, and minimizes loss of reactants. Reactants may be high value heavy metals in the catalyst layers of membrane electrode assemblies. Leak checking can be particularly challenging in larger volume fuel cell stacks where testing multi-stage processes can lead to flow spikes during the test.

Leak check stations are typically composed of two components. The first is a dual valve pressure controller, taking 1000 readings per second. The dual valve controller ensures the element under test remains at a set pressure while minimizing He usage. Meanwhile, highly sensitive PID tuning and setpoint ramping functionality help protect the membrane from flow spikes during testing. The dual valve pressure controller is paired with a low-pressure-drop mass flow meter, which characterizes the slightest leaks. With a pressure drop as low as 0.07 PSID across the unit, the flow rate measurement is more sensitive and is virtually unimpeded. These two instruments can be controlled from a single computer/PLC using options from a large list of communication protocols. Digital protocols make for easy automation and data analysis.

Solutions for other areas of fuel cell research

For the many other processes and tests that are required in areas relating to hydrogen fuel cell system R&D (e.g. catalyst verification and electrode testing) we have a range of custom mass flow and pressure solutions using a variety of technologies.

If you have any questions about solutions for hydrogen fuel cell regulation and testing, contact our applications engineers to find a solution for your process needs.

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